1. Field of the Invention
The present invention relates generally to power hand tools and more particularly, to a transmission extension adapter for use with a power hand tool for extending the length of the power hand tool and allowing adjustment of the angle in axial direction.
2. Description of the Related Art
Power hand tools are adapted for rotating a work head, such as screwdriver tip or augur tip, for working. A power hand tool usually uses a motor or air turbine to provide a rotary driving force and a transmission gear set to lower the revolving speed of the rotary driving force and to amplify the torque, thereby driving a chuck to rotate. The work head is secured to and rotated with the chuck. When compared with a manual hand tool, a power hand tool provides a high speed rotation and a high torque output, improving the working efficiency. Further, when torque control is necessary, for example, when a specific torque is required for driving a screwdriver tip to fasten a screw, the output value of a power hand tool can be set by means of limiting the output power and revolving speed.
To improve the working efficiency, an operator may use a power screwdriver to fasten screws at selected locations. Many automatic screw feeders are known for feeding screws and temporarily hold each fed screw to the front end of the screwdriver tip. A known prior art discloses an automatic feeder and a chain belt for quick connection to the front side of a screwdriver. Screws are held on the chain belt. The automatic feeder can carry the chain belt to shift one screw to the front side of the screwdriver tip. By means of moving the screwdriver tip relative to the front side of the automatic feeder, the screwdriver tip touches the screw and pushes the screw away from the chain belt toward the workpiece for fastening.
To facilitate holding, a power hand tool is generally made in the shape of a pistol and provided with a grip for holding by the user. A user usually holds a power hand tool subject to one's habit, assuring high stability. When a user is working in a wide working area, he or she can maintain the preferred working posture. However, when a user is working in a narrow working area, for example, when it is necessary to insert the screwdriver tip into a narrow gap, the working direction of the power hand tool may have to be adjusted so that the screwdriver tip can reach the work point. Under this condition, the user may be unable to keep the preferred working posture, lowering the working efficiency. When the work point is at the deep inside of a narrow gap, the user may be unable to approach the screwdriver tip of the power hand tool to the work point to fasten a screw. Under this condition, the user may have to use a low efficiency manual screwdriver to fasten the screw. If the user has to operate the manual screwdriver in a crouched posture for long time, the user will get tired soon and, the working efficiency will be lowered.